Serum leptin concentrations throughout the menstrual cycle.

Leptin is a cytokine involved in the regulation of food intake and fertility in rodents and in humans. No data exist about serum leptin serum levels during the spontaneous menstrual cycle. In this study 16 ovulatory cycles of endocrinologically normal volunteers were analyzed. Blood samples were taken on alternate days throughout the menstrual cycle for measurement of serum estradiol, progesterone, LH, FSH and leptin serum levels. No correlation of leptin values with estradiol values (r = 0.07) or progesterone values (r = 0.14) were seen. Mean leptin values during the luteal phase were significantly higher (16.67 +/- 9.45 ng/mL) compared to the follicular phase (13.50 +/- 8.75 ng/mL) (P < 0.02). A strongly positive correlation with the progression of the menstrual cycle could be seen (r = 0.91). The physiological significance of higher luteal phase leptin levels is unknown.